/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.library.dprofile;

import org.apache.commons.lang3.ArrayUtils;
import org.apache.commons.math3.analysis.interpolation.AkimaSplineInterpolator;
import org.apache.commons.math3.analysis.polynomials.PolynomialSplineFunction;
import org.apache.iotdb.library.util.Util;
import org.apache.iotdb.udf.api.UDTF;
import org.apache.iotdb.udf.api.access.Row;
import org.apache.iotdb.udf.api.collector.PointCollector;
import org.apache.iotdb.udf.api.customizer.config.UDTFConfigurations;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameterValidator;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameters;
import org.apache.iotdb.udf.api.customizer.strategy.RowByRowAccessStrategy;
import org.apache.iotdb.udf.api.type.Type;

import java.util.ArrayList;

public class UDTFSpline implements UDTF {
    AkimaSplineInterpolator asi;
    int samplePoints; // convert to is closest integer
    ArrayList<Long> timestamp = new ArrayList<>();
    ArrayList<Double> yDouble = new ArrayList<>();
    ArrayList<Double> xDouble = new ArrayList<>();
    Long minimumTimestamp = -1L;
    PolynomialSplineFunction psf;

    @Override
    public void validate(UDFParameterValidator validator) throws Exception {
        validator
                .validateInputSeriesNumber(1)
                .validateInputSeriesDataType(0, Type.FLOAT, Type.DOUBLE, Type.INT32, Type.INT64);
    }

    @Override
    public void beforeStart(UDFParameters parameters, UDTFConfigurations configurations)
            throws Exception {
        configurations.setAccessStrategy(new RowByRowAccessStrategy()).setOutputDataType(Type.DOUBLE);
        samplePoints = parameters.getInt("points");
        timestamp.clear();
        xDouble.clear();
        yDouble.clear();
    }

    @Override
    public void transform(Row row, PointCollector collector) throws Exception {
        double v = Util.getValueAsDouble(row);
        if (Double.isFinite(v)) {
            Long t = row.getTime();
            if (minimumTimestamp < 0) {
                minimumTimestamp = t;
            }
            timestamp.add(t);
            xDouble.add((Double.valueOf(Long.toString(t - minimumTimestamp))));
            yDouble.add(Util.getValueAsDouble(row));
        }
    }

    @Override
    public void terminate(PointCollector collector) throws Exception {
        if (yDouble.size() >= 4 && samplePoints >= 2) { // 4个点以上才进行插值
            asi = new AkimaSplineInterpolator();
            double[] x = ArrayUtils.toPrimitive(xDouble.toArray(new Double[0]));
            double[] y = ArrayUtils.toPrimitive(yDouble.toArray(new Double[0]));
            psf = asi.interpolate(x, y);
            for (int i = 0; i < samplePoints; i++) {
                int approximation =
                        (int)
                                Math.floor(
                                        (x[0] * (samplePoints - 1 - i) + x[yDouble.size() - 1] * (i))
                                                / (samplePoints - 1)
                                                + 0.5);
                double yhead = psf.value(approximation);
                collector.putDouble(minimumTimestamp + (long) approximation, yhead);
            }
        }
    }
}
